Mineral oil composition



Patented July 9, 1946 Herschel G. Smith, Wal Cantrell. Lansdowne,

Pennsylva lingford, and Troy L.

Pa., assignors to Gull Oil Corporation, Pittsburgh,Pa., a corporation ofnia No Drawing. Application March 19, 1945. Serial No. 583.655

11 Claims. 1

This invention relates to mineral oil compositions. More particularly,the invention is concerned with mineral lubricating oil compositions ofa character adapted to protect ferrous and other metal surfaces, towhich they are applied. from rusting and other types of corrosionin'addition to affording lubrication of such surfaces.

Simple mineral oil films aflord only a limited protection 'to metalsurfaces from rust and other types of corrosion, but do not afiord anygreat protection under severe conditions of use. Many so-calledanti-rust lubricating oils have been proposed, consisting ofmineral'oils and added constituents intended to protect metallicsurfaces from rust, tarnish or corrosion. Most of them are of ratherlimited applicability, in that while they afiord satisfactory protectionto one class of metals, they may be ineiiective, or even deleterious,with another class of metals.

These shortcomings of such mineral oils and oil compositions are seriousin manycases, particularly in cases wherein a plurality of metals mustbe simultaneously lubricated while exposed to corrosive conditions; forexample, in the case of copper-alloy bearings with steel shaft and thecase of electric motors where surfaces of both steel and copper areexposed to corrosive conditions. Moreover, many such oils show unduesensitivity to moisture and air and other substances to which they areexposed, and lubricating films of such oils do not effectively protectthe metal against rusting or tarnishing when exposed to moisture and airor other corrosive atmosph'eres. It is also found that some compoundedoils which are efiectlve as regards preventing rust, are deficient inlubricating properties.

Among the objects of the present invention is the provision of ananti-corrosion lubricating oil composition, of good lubricatingproperties, adapted to protect steel from rusting while being of itselffree from tendency to corrode copper and other metallic surfaces, andbeing in itself relatively inert and unaffected by air and moisture.

These and other objects of the invention are achieved by the provisionof a mineral 011 composition including, as a rust inhibitor, thesubstantially neutral reaction products obtained by reactingdicyclohexyl amine with acid phosphate esters of alkylated phenolscontaining at least one branched chain alkyl group, the said amine andacid phosphate esters being reacted in approximately equimolecularproportions under such conditions that the reaction product or mixturehas a DH value between 5.5 and 7.5.

2 We have found that such improved oil compositions are very efl'ectiveas anti-corrosion lubricants for metal surfaces in general. They formtightly adherent oil films on the metal, protecting the metal surfacesfrom moisture and air. In addition, the improved oil composition itselfis free from any tendency to attack copper, steel and other metals byreaction therewith or otherwise. For instance, polished or highlyfinished steel surfaces protected by establishing and maintaining theimproved oil composition on the surfaces thereof remain brightindefinitely and copper alloy bearings (which present a difficultproblem in protection from corrosion) are maintained in their highlyfinished condition even under unfavorable conditions of use. Further,copper, aluminum, zinc, tin, silver, and their alloys are alleffectively guarded against corrosion and are well lubricated by theseimproved oil compositions containing our new rust inhibitors.

In general, various improved lubricants, such as household lubricants,machine oils, gun oils. turbine oils, slushlng oils and the like areprepared, by selecting'a suitable lubricating oil or base and dissolvingthe required amount of the above described reaction products in theoils.

' In particular, the invention finds special utility in preparingimproved oil compositions of the socalled' household type, useful forlubricating light mechanisms such as electric motors, guns, etc., andcontaining relatively light (low viscosity) oils as the lubricatingbase. That is, the invention is especially well suited for improvinghighly refined lubricating oils having aSaybolt Universal viscosityranging from t0 150 at F.; minerals oils of 100 viscosity beingespecially suitable for preparing our improved oil compositions.

In general, from 0.01 to 25.0 per cent of the inhibitor is suincient toimpart to lubricating oils adequate rust-inhibiting properties. Moreconcentrated oily solutions or oil mixtures 01' the inhibitor can beprepared, as a stock solution or concentrate, which can be diluted withlubricating-oil to form a rust-preventive'lubrlcant, Usually 0.5 percent or less of the inhibitor is slimcient to impart to minerallubricating oil adequate rust-inhibiting properties for metal articlesexposed to moisture and air, but as much'as 25 per cent by weight on theoil is sometimesincorporated to afford prolonged and complete protectionfrom rust under extremely severe conditions. Such highly concentratedcompositions still retain excellent lubricating and othercharacteristics'in addition toairording practically complete extraorconditions.

rust protection under I thereof The reaction products we employ arerelatively stable compositions under ordinary conditions. At roomtemperatures some of them are heavy viscous oily liquids, while othersare soft solids which melt to oily liquids at slightly elevatedtemperatures. All of them are relatively nonvolatile. They are insolublein water and more or less water repellant. They are very resistant tohydrolysis. These reaction products or inhibitors are soluble in bothmineral and fatty oils. Their solubility varies somewhat with theparticular oil. For instance, light paraffinic oils, such as thoseemployed in making household lubricants etc. dissolve approximately 0.1per cent by weight of these reaction products, forming stable solutionsNaphthenic type mineral oils dissolve somewhat larger amounts. Ingeneral, the solubility of these reaction products or inhibitors isquite high in most oils.

These advantageous rust inhibitors can be readily prepared fromdi-cyclohexyl amine and acid phosphate esters of alkylated phenolscontaining at least one branched chain alkyl group, by reacting saidamine and acid phosphate esters together in approximately equimolecularproportions, as stated ante. In preparing our rust inhibitors orreaction products, the reaction is con'- trolled so as to producesubstantially neutral reaction products or mixtures having a pH valuebetween 5.5 and 7.5 (as measured with quinhydrone-calomel electrodeassembly).

The di-cyclohexyl amine, employed as one reactant, is a well-knownchemical compound; it being a secondary amine having the followingformula:

. our rust inhibitors may be prepared by directly reacting thedi-cyclohexyl amine with the said acid phosphate esters.

The other reactant, the and phosphate esters, are acid phosphatedi-esters of di-alkylated phenols, and may be represented by thefollowing generic formula:

wherein R represents a branched chain alkyl group, such as tertiarybutyl, secondary butyl. tertiary amyl, di-isobutyl. and like tertiaryand secondary alkyl groups, and R represents an alkyl group,advantageously a branched chain alkyl group, such as secondary butyl,tertiary butyl and the like. Thus, the acid phosphate diesters ofdi-alkylated phenols containing one or two branched chain alkyl groupsare advantageous in the practice of this invention, particularl thosecontaining two branched chain butyl groups. preferably tertiary butylgroups.

These acid phosphate esters may be prepared by various methods fromalkylated phenols containing one or more branched chain alkyl groupsattached to the phenyl nucleus in the positions indicated ante,

In particular, the acid phosphate di-esters of2-tertiary-butyl-4-secondary butyl phenol, 2,4- ditertiary-butyl phenol,2,4-ditertiary-amyl phenol, and 2-tertiary-butyl-4-tertiary-amyl phenolare advantageous for the present purposes. For instance, as shown in theillustrative examples post, di-(2,4-ditertiary-butyl phenyl) phosphatehaving the following formula:

is advantageous in preparing our rust inhibitors. These new acidphospate 'di-esters are viscous oily liquids at room temperature and arereadily soluble in mineral oils. Accordingly, mineral oil solutions ofthese acid phosphate esters may be employed in preparing concentrates ofour rust inhibitors in oil; the amine being added to such oil solutionsand reacted with the acid phosphate ester dissolved therein to form therust inhibitor in situ in the oil. In general, acid phosphate diestersof alkylated phenols containing tertiary or secondary alkyl groups areuseful and advantageous in preparing our rust inhibitors; thosecontaining a plurality of such tertiary or secondary alkyl groups beingparticularly advantageous for the present purposes. Such acid phosphatediesters are readily soluble in mineral oils and have other propertiesrendering them advantageous for the purposes of this invention.

As a class, these acid phosphate di-esters of alkylated phenolscontaining branched chain alkyl groups react readily with di-cyclohexylamine. In general, the reaction is exothermic and is quite vigorous inmost cases. In preparing our rust inhibitors, the reaction temperatureis controlled by suitable means 'to secure smooth reaction and obtainaddition products of the amine and acid phosphate ester. In doing so,the temperature of the reaction mixture is controlled by cooling orheating as required; the temperature of the reaction mixture beingmaintained below 180 F. to avoid splitting out water from the mixture.The reaction temperature is usually maintained between 140 and 170 F.during the larger portion of the reaction and within this rangeexcellent rust inhibitors are obtained; the pH value of the reactionproduct being adjusted in the final stages of the reaction within thedesired range stated ante.

The following examples illustrate advantageous methods of preparingthese rust inhibitors:

Example I.--Into a suitable kettle, equipped with means for heating,cooling and agitating the charge, there were added 474 pounds ofdi-(2,4- ditertiary-butyl-phenyl) phosphate, and then 181 pounds ofdi-cyclohexyl amine were gradually added with stirring. The reaction wasvigorous and exothermic, and the amine was added at such a gradual rateas to facilitate maintaining the reaction temperature below 180 F.; themixture being cooled if necessary to maintain it below that temperature.In this way, the reaction temperature was maintained between and F.

.5 during the larger part of the reaction. By so controlling thetemperature, the side reactions are checked, particularly the splittingout of water from the addition product and conversion of it into thecorresponding amide.

After the exothermic reaction had subsided, a further 18 pounds ofdi-cyclohexyl amine were added to the warm reaction mixture and thismixture stirred until the reaction was complete.

The substantially neutral addition product so obtained was a. heavy,viscous, oily liquid when cooled to room temperature. It had a pH valueof approximately 6.8. This amine salt or rust inhibitor had a pleasantodor and a light amber red color. It was soluble in mineral oils andother hydrocarbons. It is an excellent rust inhibitor for the presentpurposes.

Similar oily rust inhibitors having pH values within the range of 5.5and 7.5 can be readily obtained by the method described ante. Forinstance, our new rust inhibitors can also be prepared from other acidphosphate di-esters of alkyl-phenols, as well as from the particularacid phosphate ester employed in Example I. The preparation of anothersuch advantageous rust inhibitor is illustrated in the followingexample.

Example II.Here again, the reaction is carried out in a. suitablekettle. equipped with means for heating, cooling and agitating themixture, and the reaction temperature is controlled as described inExample I ante.

Into such a kettle, there were introduced 474 pounds of di-(2-tertiarybutyl-4-secondary butylphenyl) phosphate, and then 181 pounds ofdicyclohexyl amine were gradually added with stirring. The reaction wasvigorous and quite exothermic and the amine was added at such a gradualrate as to maintain the reaction temperature below 180 F.; thetemperature being maintained between 140 and 170 F., as described inExample 1.

After the exothermic reaction had subsided, a further 18 pounds of theamine were added to the warm reaction mixture and this mixture stirreduntil the reaction was complete.

The di-cyclohexyl amine salt so obtained had a pH value of approximately6.9; this salt being a substantially neutral addition product of saidamine and said acid phosphate di-ester. This salt may be represented bythe following formula:

wherein R represents a cyclohexyl group. The above amine salt or rustinhibitor was a viscous, oily liquid at room temperature. It had apleasant odor and a light amber red color. It was soluble in mineraloils and other hydrocarbons. Thus, this rust inhibitor is advantageousfor making our improved oil compositions.

In other words, the substantially neutral reaction products obtained inExamples I and II, respectively, like the amine and acid phosphateesters from which they were prepared, are soluble in mineral oils.Accordingly, we sometimes prepare concentrated solutions of these rustinhibitors in mineral oil by forming them in situ in the oil. In suchprocesses, the amine is first dissolved in the mineral oil and then theacid phosphate ester added, the mixture being stirred 75 and maintainedat the desired temperature until the reaction is complete and.themixture has a pH value within the specified range. In preparing such oilconcentrates of our rust inhibitors, sometimes additional amine is addedin the later stages to adjust the pH value as desired. The concentratesor oil solutions of inhibitor reaction products so obtained are usefuladdition agents to various types of lubricants. The preparation of suchconcentrates is illustrated in the following example.

Example III.780 pounds 01 light mineral lubricating oil having aviscosity of 100 seconds SUV at 100 F. were added to an iron vesselequipped with means for heating and cooling and agitation. The initialtemperature of the oil was F. To this oil were added 181 pounds ofdi-cyclohexyl amine, which was thoroughly mixed with the oil bymechanical agitation and the final temperature of this mixture wa 82 F.To the oil-amine mixture, 474 pounds of .di-(2,4-di-tertiary-butyl-phenyl) phosphate were added over a period of twohours, during which time the mixture was agitated and the temperature ofthe reaction mixture rose to 178 F. After stirring for one hour, the pHof the mixture was 4.8. In order to increase this value to the desiredrange, 6.0 pounds of di-cyclohexyl amine were added to the mixture andstirred and the resultant mixture had a pH of 6.1. To secure a finaladjustment, 7.0 additional pounds of di-cyclohexyl amine were added tothe mixture which after stirring for one hour and coolin to roomtemperature had a pH of 7 .4.

The 'oily mixture prepared in this Example HI can be regarded as a sortof concentrated solution which can be stored indefinitely andincorporated in lubricating oils as desired to prepare commercialanti-rust oils and improved lubricants. I

In general, the rust inhibitors 'or reaction products prepared asdescribed ante, may be dissolved in various types of mineral oils andimproved anti-rust and non-corrosive oil compositions obtained which arecapable of inhibiting or retarding the rusting of various metals asdescribed. The preparation of such improved mineral oil compositions isillustrated in the following examples. 1

Example IV.-A household-type lubricant was prepared by dissolving 0.5per cent by weight of the rust inhibitor obtained in Example I inarefined oil.

Example V.Another household-type lubricant was prepared by dissolving0.5 per cent by weight of the rust inhibitor obtained in Example II in arefl'ned oil.

The properties of tions of Examples IV and V ante as compared with theproperties of the base oil employed are as follows: i

Improved lubricant Properties Base oil Ex. IV Ex. V

Gravity, xrr 29. 2 2s. 2 28.8 Viscosity, SUV, F 102 103 103 Flash, 00,"F 330 330 330 Fire, 00, "F 365 300 360 Pour, F -30 -30 30 Color,Saybolt- +7 +5 +6 Carbon residue, per cent Trace 0.01 0. 01Neutralization No N Nil Nil These improved oil compositions haveexcellent lubricating properties.

ll k w u the improved oil composi- They also efiectively procomparedwith the base oil. For instance, in

special corrosion Test No. l, the base oil began to show rust on a steelstrip after six hours in the test, whereas after twelve days theimproved 011 showed no evidence of rust. In the other and more drasticcorrosion tests described post, these improved oils showed even greatersuperiority over the base oil as regards protecting steel 16 specimensare usually steel, copper, tin and zinc,

and-other metals against tarnish and corrosion. The results of thesespecial corrosiontests are summarizedinthe following table.

' Impovedlnbncant Special corrosion test Base oil Ex. IV -Ex. V

Steel strip Fnlk Pages... Passes. Copper str p do do Do. s iee1 strip nDo. (gopper strip do do Do. 0.

Steel strip; do ".60.... Do. Copper strip .do

The special corrosion tests referred to in the above table were asfollows: Text No. 1.-36 cc. of the oil or oil composition to be testedand 4 cc. of distilled water are put in a 1" by 6" Pyrex test tube and apolished strip of copper-or steel is immersed in the liquids. To mix theoil and water 2000 cc. of air per hour are bubbled through the mixturefrom'a point within the bottom of the test tube. The apparatus is set ina. water bath maintained at 122 F. (50 C.) and the original water levelin the tube is maintained by additions of fresh water over 24 hours. Thetest is continued for twelve days regardless of whether or not the metalstrip showed signs of corrosion. This test may also be carried out withother metal strlm such as zinc, silver and tin as well as with copper orsteel strips.

' In this test, the lower part of the metal strip is completely immersedin the water and the only way the oil can wet the metal surface is forthe oil to creep down over it against the water pressure. Accordingly,rusting immediately begins at the level where the oil and the watermeet, un-

less the metal surface is preferentially .wetted 5 by the oil; that is,-unless the oil film is capable of spreading on the metal surface anddisplacing water therefrom. I

. In other words, this test is rather a drastic one for the protectiveproperties of oils and oil compositions as regards the prevention ofrust, tarnish and corrosion. For instance, in this test; ordinarily asteel strip shows rust in about 6 hours and a copper strip will tarnishwithin approximately 12 hour when an uninhibited oilis so tested. On theother hand, generally the addition of as little as 0.1 per cent by weiht of our rust inhibitors to the oil will maintain both copper and steelstrips free from tarnish and rust for periods up to 12 days, a maximumduration of this test.

Test No. 2.In this test,- 180 cc. of the oil or oil composition to betested and 20 cc. of distilled water are placed in a 400 cc. beaker,anda polished metal strip is immersed in the oil-water 8 mixture; 2000cc. of humidified air per hour are passed through the mixture and theapparatus is maintained at 122' F. as in Test No. 1. The water level ismaintained by daily additions of distilled water and at the end of 1-2days the water layer is removed by syphon and fresh water is added. Thewater removed is analyz d to determine whether the inhibitor is beingextracted or leached from the oil solution. Fresh strips are added whenthe water is changed, so as to present a fresh metal surface to thepartially leached oil. This cycle is continued for '72 days unless thetest specimen becomes too corroded, making further testing impractical.In this test, the test although other special metals may he used.

Test No. 3.The apparatus outlined in Test No. l is employed and thetesting conditions are identical, except that water containing sodium 20chloride in the concentration equivalent to that of the total saltcontent of sea water is added instead of distilled water. This is a muchmore severe test and is conducted also for 12 days, the water levelbeing maintained in the same manner as for Test No. 1.

$0 tack by moisture and air under extremely severe conditions,particularly in Test No. 3. Further, the oil film on the metal and theoil itself are exposed to not only the leaching action of the water butalso to oxidation. Accordingly, if

8.5 rusting is prevented under such drastic condltions in these tests,there is good assurance that the inhibitor will be capable ofpreventing, or at least retarding rusting even under extremely severeservice conditions; Therefore, an inhib- 40 itor which when dissolved inan oil permits the oil to pass all three of these tests, is consideredan excellent inhibitor.

As shown ante, improved oil compositions containing our rust inhibitorshave successfully passed all of these tests. Further our improved oilcompositions in addition to having excellent anti-rust properties arealso excellent lubricants. Likewise, as shown ante, the anti-rustproperties or the improved oil may be controlled'by selecting the rustinhibitor and varying the proportions thereof incorporated in the oil.For instance, in certain special cases, where the prevailing conditionsare so extreme as to require the lubricant to be extremely highlyprotective toward metal surfaces, a higher percentage of rust inhibitoris incorporated in the oil. The following example is illustrative ofsuch embodiments of this invention.

' Example VI .In preparing one such lubricant,

00 0.3 per cent by weight of the rust inhibitor obtainedin Example I wasincorporated in a suitable oil base. The oil base selected and theimproved lubricant made from it have the following properties:

Base oil Improved oil Gravity, API Q. 5 E. 4 Viscosity SUV F 109 7Color, NiA. 1.25 1. as

" ditions, even in the presence of salt and salt water. For instance,when tested by the special corrosion Tests Nos. 1 and 3 ante, theimproved oil showed no evidence of corroding either copper or steelafter 12 days in either of the above tests. On the other hand, the baseoil allowed the steel strip to rust in approximately 8 hours in thefresh water (Test No. 1) and in about 3 hours in the salt water test(Test No. 3). Also, with the base oil, the copper strips were coatedwith a greenish deposit after overnight testing; the

copper strips being more slowly attacked thanthe steel strips butnevertheless substantially tarnished and corroded.

The specific embodiments described above are merely illustrative of thepractice of this invention and other embodiments thereof may be used asdesired; for instance, these rust inhibitors are compatible with variousother compounding in gredients and they may be added to blended oilbases or compounded lubricants to obtain other types of improvedlubricants. Improved oil compositions can be prepared from base oilscontaining varying amounts of fatty oils admixed with mineral oil, suchblends being especially useful as household lubricants. By the presentinvention, any of the previously known household or other lubricantscontaining relatively light lubricating oils can be improved by addingsmall amounts of our rust inhibitors as described.

The invention is equally applicable to heavy mineral oils, petrolatumoils, greases, and jellies; in fact to any petroleum lubricant orcoating oil, in which corrosion-preventive properties are desired. Inthe claims the term lubricant includes mineral oils, jellies forpurposes other than strict lubrication, e. g., slushing oils and gungreases.

One important application of the present invention is the prevention ofrusting in automotive and aviation engines before or after these havebeen used, either upon aging in intermittent actual awaiting completionof assembly, shipment, and other delays after engine break-in. Suchrusting is aggravated by the presence in the crankcase and crankcase-oilof moisture, sulfur, oxidation products from petroleum, tetraethyl lead,de: composition products, etc. Attempts have been made to remedy thiscondition by washing out all motor oil from the crankcase of an engineif it is to be stored for any appreciable time, or adding compoundscontaining large amounts of oiliness agents and the like. tion presentsa more economical remedy for these conditions, for corrosion iseffectively retarded under-such conditions when from 0.5 to 1.0 per centby weight of our compounds is added to. a used motor oil. Adding thehighly potent rust preventive compound during the latter part of thebreak-in period for the new engine, with operation for sufiicient timeafter addition to assure full mixing and coating of parts, will preventrusting.

Extensive tests in which the pH values of the agents of the presentinvention as employed in finished oils were varied, confirm ourdiscovery that the optimum results for a given amount of the agent inoil are secured when the pH value is maintained within the stated rangeof 5.5 to 7.5 for the compounding agent. There is usually a slight dropin pH value in the dilute finished oil solution as compared with thevalues for the compounding agents or mixtures thereof. The

finished oil (which usually contains only a small proportion of thedilute compounding agent) and the like even when used service or instorage of engines or planes The present invenless desirable results.For example, with an unduly low pH value (acid side) there is somerusting of steel surfaces by our steel strip corrosion test, whilecompositions with an excessively high pH value (alkaline side) mayproduce greenish corrosion effects on the corrosion tests with coppersurfaces and the like, although not affecting steel to any appreciableextent. The exact ad- J'ust-ment is attained in preparing the rustinhibitor compound by reacting the desired molecular proportions of thetwo agents inthe manner described, and after-the neutralization orcompounding reaction has progressed practicallyto completion, testingthe reaction product, and making any minor adjustments that arenecessary for exact control by adding the required small additionalproportion of the amines (if on the acid side of our desired range) orof theacid phosphate ester (if on the alkaline side); In measuring thepH of the anti-rust agents of the which are both substantiallywater-insoluble, the

sample is dissolved in normal butanol (which I 0 contains a small amountof water) adjusted exactly to pH 7.0. The butanol acts as a blendingagent for the water and the relatively insoluble material, but does notappreciably alter the pH value as it is of pH exactly 7 itself.Measurement is made by electrometric or colorimetric procedures; theresults agree closely.

This application is a continuation-in-part of application Serial No.504,056, now issued as Patent No. 2,371,853, of March 20, 1945.

What we claim is: a

1. An improved oil composition, efiective as a lubricant for metalsurfaces and capable of preventing corrosion thereof in the presence ofmoisture and air, comprising a petroleum lubricant containing insolution therein a small proportion of a substantially neutral additionproduct of di-cyclohexyl amine and an acid phosphate di-ester of adi-alkylated phenol having the following formula: 1 1

wherein R represents a branched chain alkyl neutral addition product ofdi-cyclohexyl amine and di-(2,4-di-tertiary-butyl-phenyl) phosphate.

3. The improved oil composition of claim 1 wherein said additionproductis a substantially neutral addition product of di-cyclohexylamine and di-(z-tertiary butyl-4-secondary butylphenyl) phosphate.

4. The improved oil composition of claim 1 wherein said addition productis a substantially neutral addition product of di-cyclohexyl amine anddi-(2-tertiary--butyl-4-tertiary-amyl-phenyl) phosphate.

5. The improved oil composition of claim 1 wherein said addition productis a substantially advantageously by weight on 11 neutral additionproduct or di-cyclohexyl amine and di-(ZA-di-tertiary-amyl-phenyl)phosphate.

6. The improved oil compomtion of claim 1 wherein said petroleumlubricant contains from 0.01 to 10.0 per cent by weight of saidsubstantially neutral addition product dissolved therein.

'1. The improved oil composition of claim 1 wherein said petroleumlubricant is a. mineral lubricating oil.

8. An improved oil composition, efiective as a lubricant for ferrous andother metal surfaces and capable of preventing corrosion thereof in thepresence of moisture and air, comprising a mineral lubricating oil and0.01 to 10.0 per cent the oil of a substantially neutral additionproduct of di-cyclohexyl amine and an acid phosphate di-ester of adi-alkylated phenol having the following formula:

wherein n represents a; branched chain alkyl 25 stantially neutraladdition product having a pH between 5.5 and 1:5 and the proportionthereof dissolved in the lubricant being sufficient to prevent rustingof ferrous metals.

9. The improved oil composition of claim 8 wherein said minerallubricating oil is a light mineral oil having a Saybolt Universalviscosi y between and 150 seconds at F.

10. The improved oil composition of claim 8 wherein the addition productis a substantially neutral addition product of di-cyclohexyl amine anddi-(2,4-di-tertiary butyl-phenyl) phosphate.

11. An improved oil composition, effective as a lubricant for ferrousand other metal surfaces and capable of preventing corrosion thereof inthe presence of moisture and air, comprisinga light mineral oil ofviscosity between 60 and seconds SUV at 100 F. containing between 0.01and 10.0 per cent .of a substantially neutral addition product ofdi-cyclohexyl amine and di-(2,4- di-tertiary-butyi-phenyl) phosphate.said addition product having a'pH value of 6.8 and the proportionthereof being sufllcient to prevent rusting of ferrous metals.

G. SMITH.

TROY L. CANTRELL.

